Process for dyeing daylight fluorescent nylon textile



United States Patent PROCESS FOR DYEING DAYLIGHT FLUO- RESCENT TEXTILE Joseph L. Switzer, Gates Mills, Ohio, assignor to Switzer Brothers, Inc., Cleveland, Ohio, a corporation of Ohio No Drawing. Application April 4, 1956,

Serial No. 575,974

7 Claim (CL li -s55) This invention relates to an improved method of imparting daylight fluorescent colors to nylon textiles. This application is a QOQlIlHUQtiQHrlIl-Pilft of my copending application for Daylight Fluorescent Nylon Textile, Serial No. 33,431, filed June 1 194 As now generally understood in the art, daylight fluorescent colors are those colors imparted by solvated organic dyes in which the dyes not only selectively reflect a predominant wave band of incident daylight (in accordance with the subtractive color theory) but als fi it light of substantially the same wave band asthe predominantly reflected wave band; such light emission is due to a fluorescent response of the solvated ye to light energy of wave l ngths Shorter than the wave lengths of the predominantly reflected wave band, Such emission of light occurs contrary to the subtractive c9191- theory which holds (correctly for most colors) that visible light energy not selectively reflected is absorbed and dissipated as heat, yli h as he rm i sed n co nection wit daylight fluorescence, is understood to be sunlight or artificial light having a substantially continuous spectrum of visible light and near ultra-violet similar to that of sunlight.

The relative brightness of daylight fluorescent colors and ordinary subtractive colors is clearly evidenced by simple spectre-photometric analyses. Whereas a subtractively colored red fabric, for example, which reflected as much as sixty per cent of the red in incident daylight would have been regardly as an extraordinarily brilliant red, red daylight fluorescent fabrics which have been produced have been found to project (emit and refle t) in excess of 120-130% of the red light in the incident daylight.

Jointly with Richard A. Ward, I discovered that the daylight fluorescene of daylight fluorescent dyestuffs observable in dilute liquid organic solvent solutions thereof could be imparted to textiles by so dyeing the fabrics that the dyes were dispersed in a solvated state substantially throughout the filaments of the fabric and were not concentrated in an unsolvated state in and on the surface of the filaments of the fabric. Qur method of daylight fluorescent dyeing, as disclosed in our copending appli cation for Daylight Fluorescent Textiles, Serial No. 430,792, filed February 13, 1942, now U. 8 Patent No, 2,606,809, comprised the steps of dissolving a daylight fluorescent dye in a dyebath comprising a strong aqueous solution of a mutual organic solvent; such as alcohol, for example, for the dye and fabric, immersing the fabric to be dyed in the dyebath while maintaining the dyebath below the temperature at which the fabric coalesced'llntil the dye became solvated throughout the fabric filaments and then quickly flushing the fabric with cool water to kill the dyeing action and prevent the aflixation of undissolved dye upon the surface of the filaments. Because the fabric filaments become a solvating agent for the dye while the fabric is immersed in the dyebath, the amount of the fabric is added to the amount of the aqueous solvent solution in determining the percentage of dye in the dyed fabric. Because such determination depends 2,759,786 Patented Aug. 21, 1956 upon an equilibrium of solution potential of the dye in the aggregative solvating agents, this system has become known as equilibrium dyeing. Normal economical dyeing practices, such as exhaustion dyeing, were avoided because of the tendency of the dye, during exhaustion of the dyebath, to build up on the surface of the fiber; while such a build up is desirable in subtractive color dyeing, it should be avoided in daylight fluorescent dyeing because of the tendency to affix the dye in an unsolvated, non-daylight fluorescent state on the surface of the filaments.

While the above system was applicable to all types of organic textile fibers, it is particularly successful in the daylight fluorescent dyeing of cellulose acetate fabrics. In dyeing other synthetic'fibers, such as nylon, by the above described equilibrium dyeing method, the results were not as satisfactory, the colors were not quite as brilliant and were far less light-fast; also their washfastness was extremely poor.

It is the object of this invention to provide a method of dyeing nylon with daylight fluorescent colors which can equal, and may actually exceed, the daylight fluorescene of daylight fluorescent cellulose acetate. A particular advantage of this invention is that the wash-fastness of daylight fluorescent nylons so dyed approaches abso lute wash-fastness and the 'light-fastness is greatly improved over that obtainable in any other daylight fluorescent textile I have seen produced. In fact, daylight fluorescent nylons produced by my method, by virtue of their showing no appreciable light sensitiveness (other than a very slight initial darkening) after forty hours in a fadeometer, have a light stability comparable to that of fabrics dyed with subtractive colored dyes other than vat dyes and thus may be marketed without notice of light sensitivity, as should usually be done with other daylight fluorescent fabrics. Another advantage of this method is that it permits, under proper conditions, exhaustion dyeing and the attendant economy of terminating a dyeing with the dyebath substantially exhausted of its dye; this contrasts with equilibrium dyeing processes in which, in commercially practiced methods, the percentage of daylight fluorescent dye in the dyebath at the end of a dyeing is as great as at the commencement of the dyeing.

I achieve the above results by employing dyes which exhibit in liquid organic solvent solutions a far lower order of daylight fluorescence than the now more comrnonly employed basic dyes such as Rhodamine B. Furthermore, the known daylight fluorescent acid dyes, which I employ in preference to daylight fluorescent basic dyes, have, when dyed as subtractive color dyes on other fabrics, been notorious for their poor light-fastness and extremely poor wash-fastness.

Another incongruity of my method is that, instead of employing mineral acids to create an aflinity of the fabric for the dyes, I employ as an agent to solvate the dye in nylon extremely strong organic acids in such strong concentrations in the dyebath that a precipitating action on the dye in the dyebath would be expected. Instead of producing the expected spotty, unlevel dyeing, I achieve extremely level dyeing. In fact, unless such strong concentrations of the solvating agent in the proper range are employed and, instead, the normal lesser concentrations of the solvating agent (at given dyebath temperatures) are employed, spotty, uneven dyeing, with non-daylight fluorescent areas will result. The use of Wetting-out agents in my process is avoided or employed with care and only after careful test dyeings, for many commercial wetting out agents, such as Igepon, for example, exhibit an unexpected precipitating action upon the dyes in the dyeb hs em lo e caus n une n ye n and -d y ht fl i r s t pot whe p ec pi ated dye s aifix d to the nylon, a waste of dyestuff insofar as daylight fluorescent dyeing is concerned.

As is evident from the foregoing discussion, in general my method consists of dyeing nylon with daylight fluorescent acid dyestuffs in a dyebath containing a high percentage of a strong organic acid as the agent for solvating the dye in the fabric. The preferred dyestuffs for dayllght fluorescent reds are the soluble alkali metal salts of sulfonated meta diethylaminophenol phthalein, such as the sodium salt thereof, having the following probable structural formula:

(airman Nwirmi 0 C--OH SOaNa Another unexpectedly excellent dyestufl which produces a brilliant greenish-yellow daylight fluorescent nylon is the sulfonic acid of 4 amino 1,8 naphthal p tolyl imide having the probable structural formula:

centration of formic acid in the dyebath varies according to the dye-bath temperature and ranges from a minimum of 12% to a maximum of at room temperature (25 C.), a minimum of 2% to a maximum of 25% at approximately boiling (95 (3.). A peculiar effect of the temperature of the dyebath temperature is that at room temperature, daylight fluorescent dyeing of nylon with those dyes in the dyebath is substantially equilibrium dyeing, that is, the nylon does not exhaust the dye from the bath except as the nylon may be considered as a diluent for reducing the percentage of dye in the bath. As the temperature of the dyebath is increased, however, the nylon tends to exhaust the dye from the bath so that, at boiling, the process becomes, for all practical purposes, an exhaustion dyeing process. Because of the general good dyehouse economy of exhaustion dyeing, it is generally preferable to carry on my process in boiling or nearly boiling dyebaths. At such temperatures, however, and particularly where the higher permissible percentages of formic acid are employed, the dyeing apparatus should be enclosed to avoid the health hazard of the dyebath fumes and vapors.

After immersion in the dyebath until the desired daylight fluorescent shade is attained, care being exercised to avoid deposition of an excessive percentage of dyestuff in the nylon whereby unsolvated dye will be affixed in the filaments and thereby destroying or minimizing the daylight fluorescence, the dyed fabric is removed, soaped 4 and rinsed, ordinary soap exhibiting the tendency to dissolve off: the nylon such unsolvated dyestufl as might otherwise be affixed on the surface thereof.

My process is adapted to the daylight fluorescent dyeing of nylon yarns in skeins or packages (spool dyeing), loose filaments and flocks, as well as Woven fabric comprised in whole or in part of nylon. In dyeing yarns and loose filaments and flocks, care should be exercised in employing the maximum permissible concentrations of acid. in the dyebath, since I have observed that the woven fabrics, particularly the tightly woven fabrics, have a lesser tendency to be parchmentized by the higher concentrations of acid. In dyeing yarns, spool or tube dyeing is generally preferable to skein dyeing in order to avoid the tangling effect of the violent dyebath upon skeins.

To obtain daylight fluorescent tints and shades intermediate the color of a single acid daylight fluorescent dye, over-dyeing is practised, either with acid daylight fluorescent dyes according to this method, or with basic daylight fluorescent dyes according to suitable procedures for such dyes, or even with non-daylight fluorescent dyes according to suitable methods for dyeing nylon with such dyes. It is generally inadvisable to attempt to dye the nylon in a dyebath containing a mixture of dyes, even acid daylight fluorescent dyes, because of the precipitating effect which one dye may have on another. Because of the danger of precipitating an acid daylight fluorescent dye upon the nylon with another dye, care should be exercised in selecting the order of successive dyeings to avoid diminution or destruction of daylight fluorescence by precipitation of the daylight fluorescent dyestufl onto the surface of the nylon. In general, the dyeing with acid daylight fluorescent dyes should precede toning with basic daylight fluorescent dyes or non-daylight fluorescent dyes.

As specific but not limitative examples of the daylight fluorescent dyeing of nylon according to my invention, the following examples are given. In all of the examples the dye was dissolved in an aqueous dyebath containing 5% by weight of technical grade formic acid. The nylon, in the form of 70-denier yarn, was wound in hundred pound lots on dye tubes and dyed in standard package dyeing equipment. The dyebath was raised from room temperature to 82.5 C. in a period of thirty minutes and then held at that temperature until no further exhaustion of the dyebath occurred. The nylon was then soaped and rinsed. A very level dyeing was obtained and there was no tendency to swell up or tighten the material on the tubes. All percentages of dyestufl are based on the weight of the nylon.

Example 1.-The dyebath contained .75% of the sodium salt of sulfonated meta diethylaminophenol phthalein. A brilliant daylight fluorescent red with a cerise tint was obtained.

Example 2.The nylon was first dyed as in Example 1, except that .9% of the acid dye was employed. The nylon was then subjected to a second dyeing in a dyebath containing 2.75% sulfonic acid of 4 amino 1,8 naphthal p tolyl imide. An extremely brilliant fiery orange shade was obtained.

Example 3.-The nylon was dyed in a bath similar to the second dyebath of Example 2, except that 3% of the acid dye was employed. The nylon was subjected to a ,second dyeing in which the dyebath contained .9% Rhodamine 6GDN, a basic daylight fluorescent dye. A third dyeing with a dyebath similar to that of the second was employed. A brilliant yellow was obtained.

Example 4.-By dyeing the nylon with simply the dyebath of the first dyeing of Example 3, a brilliant yellowgreen was obtained.

Example 5.-Nylon dyed according to Example 4 was subjected to a second dyeing in which the dyebath contained .25 Xylene Milling Green B, a non-fluorescent dyestuif. An extremely brilliant daylight fluorescent Kelly green was obtained.

It is to be understood that my invention as disclosed above may be varied by those skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.

What is claimed is:

1. The method of dyeing nylon textile material to impart a daylight fluorescent color thereto comprising the steps of immersing the nylon in a dyebath comprising an aqueous solution of formic acid and an acid daylight fluorescent dyestufl, the concentration of acid in the dyebath being within the range of from about 12% and about 55% at 25 C. to a minimum of about 2% and a maximum of about 25% at 95 C.

2. The method of claim 1 including the additional step of dyeing the nylon with a basic daylight fluorescent dye.

3. The method of claim 1 including the additional step of dyeing the nylon with a non-fluorescent dye.

4. The method of claim 1 including the further step of dyeing with a second daylight fluorescent acid dye.

5. The method of claim 1 in which the acid daylight fluorescent dye is an acid Rhodamine R.

6. The method of claim 1 in which the acid daylight fluorescent dye is a dye of the sodium salt of sulfonated meta diethylaminophenol phthalein.

7. The method of claim 1 in which the acid daylight fluorescent dye is a dye of the class consisting of the sulfonic acid of 4 amino 1,8 naphthal p tolyl imide and the sodium salt of said acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,796,011 Eckert Mar. 10, 1931 

1. THE METHOD OF DYEING NYLON TEXTILE MATERIAL TO IMPART A DAYLIGHT FLUORESCENT COLOR THERETO COMPRISING THE STEPS OF IMMERSING THE NYLON IN A DYEBATH COMPRISING AN AQUEOUS SOLUTION OF FORMIC ACID AND AN ACID DAYLIGHT FLUORESCENT DYESTUFF, THE CONCENTRATION OF ACID IN THE DYEBATH BEING WITHIN THE RANGE OF FROM ABOUT 12% AND ABOUT 55% AT 25* C. TO A MINIMUM OF ABOUT 2% AND A MAXIMUM OF ABOUT 25% AT 95% C. 